Slit line-type microwave circuit construction

ABSTRACT

A microwave slit line composed of a dielectric carrier substrate having a relatively low dielectric constant, a metal layer on one surface of the substrate and having a portion removed to form the required slit, and a dielectric plate having a relative dielectric constant &gt; OR = 8 and covering the side of the line which faces away from the substrate.

United States Patent Marquardt et a].

[ 1 June 24, 1975 1568,000 3/l97l D'Aboville 333/84 M 3,602.845 8/197] Agrios 333/84 R OTHER PUBLICATIONS [75] Inventors: Jurgen Marquardt, Backnang; Erich Pivit, Allmersbach Im Tal. both Of Cohn, S. 8., Sandwich Slot Line," MTT-l9, 9-1971, Germany pp. 773-774. [73] Assignee: Licentia Patent-Verwaltungs-GmbH, Cob, Slot Line on A Dielecmc Substrate,

Frankfurt am Main, Germany M11247 104969 Robinson et al., Slot Llne Apphcatlon To Mmiature [221 Fl1ed= Ferrite Devices, MTl'-17, l2-l969, 1097-1101.

121 App]. No.2 419,294

Primary E.raminerAlfred E. Smith Assistant ExaminerWm. H. Punter (30] Foreign Application Priority Data Anameyy Agent. or Firm Spencer & Kaye Nov. 30, l972 Germany 2258594 NOV. 30 I972 Germany 438665[U] [52] US CL 333/84 333,84 M A microwave slit line composed of a dielectric carrier [51] lnt'cl I i 3/02.'Hmp 3/08 substrate having a relatively low dielectric constant. a [58] Field of U 333/84 R 84 M metal layer on one surface of the substrate and having a portion removed to form the required slit, and a di- [56] Reierences cued electric plate having a relative dielectric constant 2 8 and covering the side of the line which faces away UNITED STATES PATENTS from the Substrate. 3.543,!98 11 1970 Stopper 333/84 M 0 3.560.893 2/1971 Wen 333/84 M 7 Claims. 2 Drawing Figures 4 as D\\\\ d SLIT LINE-TYPE MICROWAVE CIRCUIT CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates to a circuit arrangement of the type including a dielectric carrier substrate having a relatively low dielectric constant and a metal lamination applied to one surface side for effecting symmetrical microwave conduction.

In the microwave art use is made of slit lines which are formed by applying an appropriate-metal lamination to a dielectric substrate serving as the carrier element. The carrier material of such a structure is a dielectric material with a relative dielectric constant greater than 8. This enables a wave to be conducted along the symmetrical slit line and to the extent possible, no radiation occurs. Such an arrangement can also be modified in that the slit line is applied to one side of the ceramic carrier and microwave strip lines are applied to the opposite side. Such an arrangement is disclosed, for example, in IEEE Transactions, M'I'T, December, 1970, page 1092.

The processing of dielectric material having a dielectric constant e z 8, i.e. ceramic material, is known to be difficult and expensive.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an arrangement of this type which can be produced in a very simple manner and which eliminates the above-mentioned drawback.

The objects according to the invention are achieved, in a circuit device including a substrate having a low dielectric constant e and a metal layer disposed on one surface of the substrate and having a portion removed to form a symmetrical microwave slit line, by the provision of a dielectric cover plate covering the side of the line which faces away from the substrate, the dielectric plate being of a material with e 8.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional perspective view of one preferred embodiment of the invention.

FIG. 2 is a view similar to that of FIG. 1 of a second preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit element shown in FIG. 1 has, as its base, a dielectric substrate 1 having a relatively low dielectric constant e in the range from I to about 6.

A suitable material for this purpose is, for example polytetra fluoroethylene. This substrate is provided in a known manner, as by lamination or deposition, with a metal layer in order to produce the desired conductive paths. In the illustrated embodiment the upper surface of substrate I of thickness D is provided with a metal lamination or plating 4, 5, which is normally made of copper. The layers are provided in such a way that a narrow longitudinal slit with a width b is produced between the two parts 4 and 5.

This slit line 2 is now covered with a dielectric plate 3 which has a dielectric constant 5, equal to or greater than 8. The plate 3 which has a thickness d, is preferably adhesively secured, as by glue with Epoxy-Resin, to the arrangement. The width a of this covering plate 3 is a multiple of the slit width b of slit line 2. The propagation of the waves in the slit line takes place substantially within the dielectric plate 3. The material of the cover plate 3 is ceramic for example A1 0 In a preferred embodiment it may also consist of a magnetized ferrite, for example a Magnesium-Manganese-Ferrite or an Yttrium-Iron-Garnet.

On the underside of the dielectric substrate 1 a microwave strip line 6 is additionally applied in a known manner in the illustrated embodiment. In order to produce certain circuits it is necessary to connect the strip line 6 with the slit line 2. This can be effected in a simple manner by providing the substrate 1 with a bore 7 and metal-plating the bore in order to produce the desired electrical contact. Thus the asymmetrical strip line 6 is coupled to the symmetrical slit line 2. It is understood that for complicated circuits a plurality of such connections are possible between the strip lines applied to the underside of substrate 1 and the slit line 2 disposed on the upper side of the substrate 1. Since the strip line 6 conducts an asymmetrical wavetype and the slit line 2 a symmetrical wavetype, it is possible to produce, in a simple manner, decoupled circuits, for example push-pull mixers with modulators. This would merely involve simple substitution for hybrid circuits.

In a further embodiment of the invention, as shown in FIG. 2, the arrangement is so designed that two circuit arrangements are attached one on top of the other so that a common dielectric plate 3 can be used for two difi'erent slit lines 2 and 2'. The second slit line 2 is defined by plating portions 4 and 5' on a second substrate 1'. Plate 3 is also adhesively secured to line 2'. This makes it possible to accommodate complicated circuits in a compact space, the production of the individual conductive paths being effected in a known, simple manner in that the carrier substrates 1 and 1' are copper laminated or plated polytetrafluoroethylene and the conductive paths desired on the two surface sides are produced by etching away the undesired metal areas. The brittle and difficult to process ceramic material for the cover plate 3 is then glued to the slit lines 2 and 2' in a simple manner so that the previously required difficult and time consuming steps for processing the ceramic material are eliminated.

One operative embodiment of the arrangement shown in FIG. 1 was built up in the following manner suitable for the the frequency range of 4-9 GHz:

the parts 1, 4, 5 and 6 are copper plated fiber glass,

polytetrafluoroethylene part 3 consists of an A1 0;, ceramic,

part 6 is a 500. strip line,

the hole 7 is plated through with copper,

the slot line 2 has a dimension b of I pm,

the thickness D of the arrangement is 438 pm,

the thickness d of the ceramic plate 3 is 635 pm,

the width a of the plate 3 is 25 mm.

It will be understood that the above description of the present invention is susceptible to various modifica tions, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

I. In a circuit device including a dielectric carrier substrate having a relatively low dielectric constant a and a first metal layer on one surface side for forming a symmetrical microwave line, the improvement wherein said line is in the form ofa slit line, said device comprises a. a dielectric plate bonded to said first metal layer and covering the side of said line which faces away from said substrate; the dielectric constant a of said dielectric plate being relatively high and having a value of at least 8;

b. a second metal layer disposed on the side of said substrate facing away from said slit line. said second metal layer defining an asymmetrical strip line;

c. means defining a bore extending through said substrate between its side carrying said slit line and its side carrying said strip line; and

d. a third metal layer disposed on the walls of said bore and coupling said lines together.

2. A device as defined in claim 1 wherein said plate is dimensioned to extend beyond the edges of said slit line by a distance equal to at least a multiple of the width of said slit line.

3. A device as defined in claim 2 wherein said plate is of ceramic material.

4. A device as defined in claim 2 wherein said plate is of a magnetized ferrite.

5. A device as defined in claim 1 wherein said plate is glued to said metal layer forming said slit line.

6. A device as defined in claim 1 wherein said carrier substrate is made of polytetraflouroethylene, and said first and second metal layers are constituted by copper plating, and said slit line is produced by etching away the undesired portions of the plating.

7. A device as defined in claim 1 comprising means including a fourth metal layer defining a second slit line and wherein said plate also covers said second slit line. 

1. In a circuit device including a dielectric carrier substrate having a relatively low dielectric constant Epsilon r1 and a first metal layer on one surfaCe side for forming a symmetrical microwave line, the improvement wherein said line is in the form of a slit line, said device comprises a. a dielectric plate bonded to said first metal layer and covering the side of said line which faces away from said substrate; the dielectric constant Epsilon r2 of said dielectric plate being relatively high and having a value of at least 8; b. a second metal layer disposed on the side of said substrate facing away from said slit line, said second metal layer defining an asymmetrical strip line; c. means defining a bore extending through said substrate between its side carrying said slit line and its side carrying said strip line; and d. a third metal layer disposed on the walls of said bore and coupling said lines together.
 2. A device as defined in claim 1 wherein said plate is dimensioned to extend beyond the edges of said slit line by a distance equal to at least a multiple of the width of said slit line.
 3. A device as defined in claim 2 wherein said plate is of ceramic material.
 4. A device as defined in claim 2 wherein said plate is of a magnetized ferrite.
 5. A device as defined in claim 1 wherein said plate is glued to said metal layer forming said slit line.
 6. A device as defined in claim 1 wherein said carrier substrate is made of polytetraflouroethylene, and said first and second metal layers are constituted by copper plating, and said slit line is produced by etching away the undesired portions of the plating.
 7. A device as defined in claim 1 comprising means including a fourth metal layer defining a second slit line and wherein said plate also covers said second slit line. 